1. Field of the Invention
The invention is directed to compositions and methods for removing emulsified oils from the quench waters used in ethylene manufacturing operations; and more particularly, the invention is directed to a method of removing emulsified oils from the quench waters of an ethylene water quench tower using water-soluble polymers dispersed in a concentrated salt media.
2. Description of the Prior Art
In ethylene manufacturing plants, a water quench column cools the gas leaving a primary fractionator. In many plants, a primary fractionator is not used, and the feed to the water quench column is directly from a transfer line exchanger. In either case, if the quench process is either incomplete or too severe, excessive product degradation can occur, resulting in fouling of both the quench tower and the downstream compressors.
In the base of the tower, hot quench water is separated from condensed hydrocarbon oils, such as, pyrolysis gasoline, which have condensed along with the dilution steam. Once the oils are removed from the water, the water can be recycled to a dilution steam generator system, while the oil can be returned to the primary fractionator as reflux. However, the oil and water can be emulsified, and poor separation of the two phases will increase fouling in the dilution steam generator and quench water exchangers, as well as increasing stripping steam requirements. In addition, because the water absorbs acidic compounds, corrosion is a potential problem.
In the ethylene manufacturing industry, quench waters generated in ethylene manufacture operations contain heavy, middle, and light hydrocarbons. The different hydrocarbons found are due to the different feeds of a particular plant. A plant that cracks heavy oils compared to a plant that cracks only ethane will have much heavier hydrocarbons condensed and emulsified in the quench water. In general, the hydrocarbons are aromatic compounds, such as naphthalene and anthracene or light hydrocarbons composed of pentanes and piperylenes.
These emulsified hydrocarbons are different from those that are found in oil field produced water. Oil field produced waters contains asphaltenes, heavy polyaromatic hydrocarbons, resins and very long chain paraffins. These hydrocarbons are almost never found in ethylene quench waters.
These quench water-oil emulsions can be broken with the demulsifiers of the present invention. The demulsifing compositions and methods of the present invention provide faster, more complete water-oil separation, better level control in the unit, lower stripping steam requirement and less downstream fouling.